Representative Rush D. Holt Jr. of New Jersey, a research physicist who became Congress’s chief advocate for scientific research over eight terms, announced on Tuesday that he is not seeking re-election this year.

Mr. Holt, 65, joins 12 fellow Democrats, and 21 Republicans, in an exodus from the House. But in an interview, he said he was not bemoaning what he acknowledged was “a certain level of dysfunction” in Congress.

“Congress, even with its frustrations, is the greatest instrument for justice and human welfare in the world,” he said. “The stories trying to puzzle out why someone would do something else are based on this rather narrow way of thinking that the only purpose for a member of Congress is to be re-elected. I’ve never viewed it that way, and I think everybody who’s worked with me knows that I think there are a lot of things that I can and should be doing.”

Mr. Holt’s retirement is not expected to affect the Democrats’ chances in 2014; a seat that he barely wrested from a Republican in 1998 has been made reliably Democratic in two rounds of redistricting.

Mr. Holt is perhaps most popularly known as the five-time “Jeopardy!” champion who later won a celebrity round against Watson, the IBM supercomputer. In and around Princeton, where he had been assistant director of the Plasma Physics Laboratory, bumper stickers on Priuses proudly proclaim “My Congressman IS a Rocket Scientist.”

He has consistently pushed for more money for scientific research, and better science education, securing $22 billion for research in the stimulus bill, and grants of $16,000 for students who prepare to teach math, science or foreign languages.

“I’m not sure we have anyone in the Congress with his level of deep understanding of what it is going to take for the American scientific enterprise to thrive in the future,” said Shirley M. Tilghman, a molecular biologist and former president of Princeton.

Among his other accomplishments, Mr. Holt said he was proudest of getting “tens of millions” of dollars for suicide prevention among members of the military, and for securing state matching programs for land and water conservation. He also helped arrange citizenship for the family of a Pakistani man killed in a hate crime in the days after the Sept. 11 attacks.

Particularly as Tea Party Republicans challenged the science of climate change in recent years, Mr. Holt argued vociferously for the importance of what he called “evidence based” debates.

“We all talk about making history in Congress, but Rush not only made history, he made progress,” said the House Democratic leader, Representative Nancy Pelosi of California.

The 12th Congressional District, in central New Jersey, had been in Republican hands for more than 30 years when Mr. Holt ran in 1998, in the middle of the debate over the impeachment of President Bill Clinton.

Mr. Holt, who had never held public office, narrowly nudged out the Republican incumbent, Michael Pappas, who had stood on the floor of the House and sung a tribute to the special prosecutor: “Twinkle, Twinkle, Kenneth Starr, now we know how brave you are.”

Mr. Holt pushed for safeguards to touch-screen voting machines, and Internet privacy in the face of widened government surveillance.

Running in the primary last year to fill the vacancy left by Senator Frank R. Lautenberg’s death, Mr. Holt showed flashes of frustration with the celebrity candidacy of Mayor Cory A. Booker of Newark, arguing that he had more experience and was the “most progressive” Democrat in the race. Mr. Holt came in third, with 17 percent of the vote, just behind Representative Frank Pallone.

The open seat is expected to draw the interest of several Democratic legislators.

“You will have a real primary,” said Brad Lawrence, a Democratic strategist who has worked for Mr. Holt.

Among the Democrats mentioned are State Assemblyman Reed Gusciora and State Senator Linda R. Greenstein — though Democrats in the New Jersey Legislature might be concerned about losing Ms. Greenstein’s seat, which was in Republican hands before she won it. Assemblyman Upendra J. Chivukula ran against Leonard Lance in a neighboring district in 2012, but lives in Mr. Holt’s.

One possible Republican candidate is Scott Sipprelle, a venture capitalist who challenged Mr. Holt in 2010, winning 46 percent of the vote. Alieta Eck, a physician who lost the Republican primary for Mr. Lautenberg’s seat last year, filed papers last month to run against Mr. Holt.

Mr. Holt’s decision means the state will elect representatives to three open seats this year. Another Democrat, Rob Andrews, announced two weeks ago that he was resigning to take a position at a law firm based in Philadelphia. A Republican, Jon Runyan, announced in November that he was not seeking re-election.

Mr. Holt’s retirement was not the only surprising announcement made by House Democrats on Tuesday: Representative Gloria Negrete McLeod of Chino, Calif., said she would step down after a single term this year and run instead for the San Bernardino County Board of Supervisors.

While Mr. Holt had an unusual background for Congress, he also has a political pedigree. His father, Rush D. Holt Sr., was the youngest person popularly elected to the United States Senate. His mother, Helen F. Holt, was the first woman appointed secretary of state in West Virginia.

Mr. Holt said that when he told his mother, now 101 and living in Washington, of his retirement, she asked whether it was really time, saying she thought there were a lot more things he could do in Congress. “By that argument,” he said, “I would stay until my dotage.”

Correction:

An earlier version of this article misstated Representative Rush D. Holt Jr.'s election record. He had not held office before being elected to the House in 1998, but he did run for Congress in 1996; thus, it is not the case that he "had never sought public office before 1998."

Correction:

An earlier version of this article misstated the number of open House seats from New Jersey in the fall election. It is three, not two.

A version of this article appears in print on , on Page A15 of the New York edition with the headline: New Jersey Congressman Won’t Seek a 9th Term. Order Reprints | Today’s Paper | Subscribe

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